1. Field of the Invention
The present invention relates to a thermal printer mounted on, e.g., a register, and a printing device.
2. Description of the Related Art
There has been known a thermal printer mounted on, e.g., a register or the like, to print various pieces of information in a receipt made of thermosensitive paper. Normally, for example, as described in Jpn. Pat. Appln. KOKAI Publication No. 11-286147, the thermal printer includes a thermal head for heating the thermosensitive paper and a platen roller for pressing the thermosensitive paper to the thermal head.
In such a thermal printer, when there is no more thermosensitive paper, a user must open a cover to supply new thermosensitive paper. Accordingly, a recent thermal printer may include a release button for easily opening a cover by a single action.
However, the conventional thermal printer has used a coil spring to return the pressed release button to its original position. Thus, a space must be provided to receive the coil spring in the cover, which has caused enlargement of the thermal printer. An object of the present invention to provide a compact thermal printer which enables easy opening of a cover by a single action.
In the above thermal printer, the thermosensitive paper passes between the thermal head and a platen, and printing is carried out on the thermosensitive paper by heat added to the thermal head. The thermosensitive paper is normally wound into a roll shape, and an opening/closing cap in an upper part of the casing must be opened when the thermosensitive paper is replaced.
The following problem has occurred in the above thermal printer. That is, the thermal head is disposed on the casing side, the platen is disposed on the cap side, and the thermal head and the platen normally come into contact with each other when pressed. Consequently, when the cap is opened/closed, the platen interferes with the casing side. Thus, a complex operation of opening/closing the opening/closing cap after shifting it in a direction away from the thermal head, or the like is necessary.
It is therefore an object of the present invention to provide a thermal printer which can open an opening/closing cap by an easy operation when thermosensitive paper is replaced.
As described in U.S. Pat. No. 3,118,469, there has been known a thermal printer in which a cover is fixed to a printer main body to be rotated and opened/closed, a thermal head is disposed on a printer main body side, and a platen roller is disposed on a cover side. In this case, to obtain a desired conveying force and desired printing pressure, the thermal head is pressed to the platen roller in a closed state. In this thermal printer, the printer main body and the cover are engaged with each other by a locking mechanism to maintain the closed state, and the engagement of the locking member is released to move the cover away from the printer main body, thereby setting an opened state. However, in the thermal printer of this configuration, as the thermal printer is pressed to the platen roller in the closed state to generate a frictional force, even if the engagement of the locking member is released, this frictional force produces resistance, making opening/closing difficult. It is therefore an object of the present invention to provide a thermal printer which enables easy and smooth opening/closing.
There has been known a printing device which includes a first printing part positioned on a sheet conveying-direction downstream side in a sheet conveying path and a second printing part positioned on a sheet conveying-direction upstream side in a device main body, and performs printing on both surfaces of a sheet by the first and second printing parts.
For example, as described in U.S. Pat. No. 6,784,906, the first printing part includes a first thermal head as a printing head, and a first platen roller arranged to face the first thermal head via the sheet conveying path and to convey the sheet. The second printing part includes a second thermal head as a printing head, and a second platen roller arranged to face the second thermal head via the sheet conveying path and to convey the sheet.
An opening/closing member is disposed in the device main body, and sheets are replenished by opening this opening/closing member. The first platen roller of the first printing part and the second thermal head of the second printing part are fixed to the opening/closing member. By closing the opening/closing member, the first thermal head is pressed to the first platen roller, and the second thermal head is pressed to the second platen roller. The first and second thermal heads are pressed by spring forces of first and second spring members.
However, as pressing directions of the first and second thermal heads to the first and second platen rollers are reverse to each other, there has conventionally been a problem that their pressing forces affect each other, and it is difficult to set head loads of the first and second thermal heads on the first and second platen rollers to proper states, making it impossible to expect good printing.
An object of the present invention to provide a printing device which can properly obtain head loads of first and second printing heads on first and second platens.